Rectification using a diode may lead to power loss due to a forwarding voltage of the diode. To reduce the power loss, a switching operation of a synchronous rectification MOSFET including a body diode may be used.
Ideally, rectification using a synchronous rectification MOSFET includes detecting conduction of a body diode, turning on the synchronous rectification MOSFET connected to the conducting body diode, and turning off the synchronous rectification MOSFET before the body diode becomes blocked. Thus, it is important to control the switch timing of the synchronous rectification MOSEFET. However, accurately anticipating the turn-off time of the synchronous rectification MOSFET is not easy.
Even if the synchronous rectification MOSFET is turned off when electric currents flowing through the synchronous rectification MOSFET are detected and become zero current, it is still difficult to accurately detect the current flowing through the synchronous rectification MOSFET. This is because On resistance of the synchronous rectification MOSFET is very low, and thus, the current is weak with respect to noise and is likely to be distorted.